JP7195678B1 - LAMINATED SHEET AND FOOD PACKAGING CONTAINER - Google Patents

Abstract

Kind Code: A1 An object of the present invention is to provide a laminated sheet containing calcium carbonate particles at a high concentration and having less variation in moldability, mechanical properties and appearance. The present invention is a laminated sheet comprising an inner layer and a pair of outer layers laminated on both sides of the inner layer, wherein the inner layer contains an inorganic filler and a thermoplastic resin, and the outer layer contains a thermoplastic resin. A plastic resin is included, the inorganic filler includes calcium carbonate particles, the content of the calcium carbonate particles in the inner layer is 40.0% by mass or more and 80.0% by mass or less, and the calcium carbonate particles are The ratio of the thickness of each outer layer constituting the pair of outer layers, which is surface-treated with a surface treatment agent containing at least one of sulfonic acid and its salts, or a phosphate ester, is relative to the total thickness of the laminated sheet. is 2.0% or more and 20.0% or less. [Selection figure] None

Description

TECHNICAL FIELD The present invention relates to a laminated sheet and a food packaging container.

Conventionally, a laminated sheet is known which includes an inner layer containing an inorganic filler and a thermoplastic resin, and a pair of outer layers laminated on both sides of the inner layer and containing a thermoplastic resin.

In recent years, from the viewpoint of environmental protection, it is desired to reduce the content of resin components in various resin products.

On the other hand, Patent Document 1 discloses a thermoplastic resin-containing laminate comprising an inner layer and a pair of outer layers laminated on both sides of the inner layer, wherein the content of calcium carbonate particles in the laminate is 50.0. Laminates with greater than % by weight are disclosed. Further, in Patent Document 1, in order to suppress the generation of voids at the interface between the calcium carbonate particles and the thermoplastic resin, the calcium carbonate particles are subjected to surface treatment such as silane coupling agent treatment and calcium stearate treatment. It is also disclosed that The laminate of Patent Document 1 is preferable for environmental protection because it contains calcium carbonate particles at a high concentration. Further, according to Patent Document 1, it is supposed that a laminate having excellent moldability can be obtained.

Japanese Patent No. 6857428

However, since the laminate disclosed in Patent Document 1 contains only calcium carbonate particles having a small particle size, uneven distribution of the calcium carbonate particles tends to occur due to poor dispersibility during kneading. When the calcium carbonate particles are unevenly distributed in the resin composition as described above, there is a problem that the resulting laminate and its molded product tend to vary in moldability, mechanical properties and appearance.

In addition, in a resin molding containing a thermoplastic resin and an inorganic filler, voids often occur around the inorganic filler. This hollow portion may affect the molding workability, mechanical properties and appearance of the resin molding.

For example, if the porosity of the resin portion of the resin molded body is high, the resin molded body is usually less likely to crack because there are many places where the deformation inside the resin molded body can escape when a strong external force is applied to the resin molded body. On the other hand, when the porosity of the resin is low, there is little escape from the deformation in the resin molded body when a strong external force is applied to the resin molded body, so the resin molded body is usually less likely to crack. Thus, the porosity of the resin may affect the molding workability, mechanical properties and appearance of the resin molding.

In general, inorganic fillers are harder than thermoplastic resins. For this reason, when the resin molded article contains a large amount of inorganic filler, the effect of the porosity of the resin on molding processability, mechanical properties and appearance tends to be more pronounced. That is, when the resin molded article contains a large amount of inorganic filler, the resin molded article has less escape space for deformation due to the hard inorganic filler. likely to have a greater impact on

The laminate disclosed in Patent Document 1 is a laminate produced for the purpose of reducing the generation of voids at the interface between calcium carbonate particles and a thermoplastic resin. Moreover, the surface treatment disclosed in Patent Document 1 reduces the porosity. For this reason, the laminate disclosed in Patent Document 1 may not have sufficient moldability, mechanical properties, and appearance due to an inappropriate porosity.

As described above, conventional laminates have the problem that the moldability, mechanical properties, and appearance tend to vary due to the uneven distribution of calcium carbonate particles and the small porosity of the resin portion. .

The present invention has been made in view of the above circumstances, and an object thereof is to provide a laminated sheet containing calcium carbonate particles at a high concentration and having less variation in moldability, mechanical properties and appearance.

The present inventors have found that when an inorganic filler containing calcium carbonate particles is subjected to a specific surface treatment, the dispersibility and reactivity of the inorganic filler containing calcium carbonate particles are enhanced, and the porosity of the inner layer becomes appropriate. We have found that the laminate sheet has improved moldability, mechanical properties and appearance. For this reason, the present inventors have found that a laminate sheet containing an inorganic filler that has undergone the above-described surface treatment can provide a laminate sheet that is less likely to vary in moldability, mechanical properties, and appearance. I have perfected my invention. More specifically, the present invention provides:

(1) A laminated sheet comprising an inner layer and a pair of outer layers laminated on both sides of the inner layer,
The inner layer contains an inorganic filler and a thermoplastic resin,
The outer layer comprises a thermoplastic resin,
The inorganic filler comprises calcium carbonate particles,
The content of the calcium carbonate particles in the inner layer is 40.0% by mass or more and 80.0% by mass or less,
The calcium carbonate particles are surface-treated with a surface treatment agent containing at least one of sulfonic acid and its salts , or a phosphate ester,
The thickness ratio of each outer layer constituting the pair of outer layers is 2.0% or more and 20.0% or less with respect to the total thickness of the laminated sheet.
Laminated sheet.

(2) The laminated sheet according to (1), wherein the thermoplastic resin is a polypropylene-based resin and/or a polyethylene-based resin.

(3) The measured plane occupancy MPO of the inorganic filler in at least one cut surface of the inner layer is the theoretical plane occupancy of the inorganic filler in the cut surface calculated based on the content of the inorganic filler in the inner layer. The laminated sheet according to (1), which is lower than TPO by 2% or more.

(4) the polyethylene-based resin includes high-density polyethylene and linear low-density polyethylene;
MFR (190 ° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) of the high-density polyethylene is 5 g / 10 minutes or more and 15 g / 10 minutes or less,
MFR (190 ° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) in the linear low density polyethylene is 0.5 g / 10 minutes or more and 1.5 g / 10 minutes or less,
The laminated sheet according to (2), wherein the mass ratio of the high density polyethylene and the linear low density polyethylene is 90:10 to 50:50.

(5) the thermoplastic resin contained in the inner layer is a polypropylene resin;
The laminated sheet according to (1), wherein the polypropylene resin is a polypropylene homopolymer and/or a polypropylene block polymer.

(6) The laminated sheet according to (1), wherein the calcium carbonate particles are heavy calcium carbonate particles.

(7) The sulfonic acid is one or more sulfonic acids selected from the group consisting of alkylsulfonic acid, alkylbenzenesulfonic acid having an alkyl group with 2 or more carbon atoms, toluenesulfonic acid, and xylenesulfonic acid, ( 1) The laminated sheet as described in 1).

(8) The laminated sheet according to item (1), wherein the phosphate ester is polyoxyethylene lauryl ether phosphate.

(9) The laminated sheet according to any one of (1) to (8), which is a laminated sheet for vacuum forming.

(10) A food packaging container formed from the laminated sheet according to (9).

ADVANTAGE OF THE INVENTION According to this invention, the lamination sheet which contains calcium carbonate particles at a high density|concentration and is hard to produce the variation in moldability, a mechanical property, and an external appearance is provided.

Embodiments of the present invention will be described below, but the present invention is not limited thereto.

[Laminated sheet]
The laminated sheet of the present invention is a sheet having at least three layers, comprising an inner layer and a pair of outer layers laminated on both sides of the inner layer. Hereinafter, of the pair of outer layers, the outer layer laminated on one surface of the inner layer is also referred to as "first outer layer", and the outer layer laminated on the other surface of the inner layer is also referred to as "second outer layer".

The laminated sheet of the present invention satisfies all of the following requirements. The first outer layer and the second outer layer may have the same or different configurations as long as the following requirements are satisfied.
(Requirement 1) The inner layer contains an inorganic filler and a thermoplastic resin.
(Requirement 2) The outer layer contains a thermoplastic resin.
(Requirement 3) The inorganic filler contains calcium carbonate particles.
(Requirement 4) The content of the calcium carbonate particles in the inner layer is 40.0% by mass or more and 80.0% by mass or less.
(Requirement 5) The calcium carbonate particles are surface-treated with a surface-treating agent containing at least one of sulfonic acid and its salt , or a phosphate ester.
(Requirement 6) The thickness ratio of each outer layer constituting a pair of outer layers is 2.0% or more and 20.0% or less with respect to the total thickness of the laminated sheet.

The laminated sheet of the present invention has a main technical feature in the composition of its inner layer.
Specifically, the inorganic filler contained in the inner layer contains calcium carbonate particles, the content of the calcium carbonate particles in the inner layer is 40.0% by mass or more and 80.0% by mass or less, and the inorganic filler is sulfonic acid and The point is that the surface is treated with a surface treatment agent containing at least one of its salts or a phosphate ester (requirements 3 to 5).

In the laminated sheet of the present invention, when the inorganic filler containing calcium carbonate particles is subjected to a specific surface treatment, the dispersibility and reactivity of the inorganic filler are enhanced, so that the porosity of the inner layer becomes appropriate, resulting in deformation of the inner layer. It was completed by discovering that the escape space of the laminated sheet becomes appropriate, and as a result, the moldability, mechanical properties and appearance of the laminated sheet are improved.

In the present invention, the "appearance of the laminated sheet" is a concept including the surface state of the laminated sheet.
In the present invention, the phrase "variation in the appearance of the laminated sheet is suppressed" is a concept that includes almost no or no irregularities, deformation, or breakage on the entire surface of the laminated sheet. be.

The appearance of the laminated sheet is evaluated, for example, by the method disclosed in the Examples.

In the present invention, the "mechanical properties of the laminated sheet" is a concept including the tensile strength of the laminated sheet.
In the present invention, "variation in mechanical properties of the laminated sheet is suppressed" is a concept that includes small variation in tensile strength of the laminated sheet.

The mechanical properties of the laminated sheet are evaluated, for example, by the methods disclosed in the Examples.

In the present invention, the "moldability of the laminated sheet" is a concept indicating ease of molding from the laminated sheet into a molded container. The moldability of the laminated sheet is determined by the difference between the actual dimensions of the molded container and the target dimensions, and the degree of distortion in the shape of the molded container.
In the present invention, the phrase "variation in molding processability of the laminated sheet is suppressed" includes a concept that the difference between the actual dimensions of the molded container and the target dimensions is small, and that the amount of distortion in the shape of the molded container is small. is.

The moldability of the laminated sheet is evaluated, for example, by the method disclosed in Examples.

The configuration of the laminated sheet of the present invention will be described in detail below.

(1) Inner layer The inner layer contains an inorganic filler and a thermoplastic resin. That is, the inner layer is made of a resin composition containing an inorganic filler and a thermoplastic resin. The outer layer, which will be described later, contains a thermoplastic resin, but does not intentionally contain an inorganic filler, and does not substantially contain an inorganic filler.

<Inorganic filler>
Examples of inorganic fillers include salts (carbonates, sulfates, silicates, phosphates, borates), oxides, and hydrated metals (calcium, magnesium, aluminum, titanium, iron, zinc, etc.). Particles of matter are used.

Specific examples of inorganic fillers include calcium carbonate, magnesium carbonate, zinc oxide, titanium oxide, silica, alumina, clay, talc, kaolin, aluminum hydroxide, magnesium hydroxide, aluminum silicate, and magnesium silicate. , calcium silicate, aluminum sulfate, magnesium sulfate, calcium sulfate, magnesium phosphate, barium sulfate, silica sand, carbon black, zeolite, molybdenum, diatomaceous earth, sericite, shirasu, calcium sulfite, sodium sulfate, potassium titanate, bentonite, water Particles such as lastonite, dolomite, and graphite are used.

The shape of the inorganic filler is not particularly limited, but may be particulate (spherical, irregular, etc.), flake, granular, fibrous, or the like.

When the inorganic filler is particulate, the lower limit of the particle size of the inorganic filler is not particularly limited, but the average particle size is preferably 0.7 μm or more, more preferably 1.0 μm or more. When the inorganic filler is particulate, the upper limit of the particle size of the inorganic filler is not particularly limited, but the average particle size is preferably 6.0 μm or less, more preferably 5.0 μm or less. In the present invention, the "average particle size" means a value calculated from the measurement results of the specific surface area by the air permeation method according to JIS M-8511. As a device for measuring the average particle diameter, for example, a specific surface area measuring device “SS-100 type” manufactured by Shimadzu Corporation can be preferably used.

Inorganic fillers used in the inner layer include calcium carbonate particles. As the calcium carbonate particles, for example, heavy calcium carbonate, light calcium carbonate, and the like are used. The calcium carbonate particles used in the inner layer preferably contain ground calcium carbonate particles, more preferably consist of ground calcium carbonate particles.

Here, “heavy calcium carbonate” means calcium carbonate obtained by mechanically pulverizing (dry method, wet method, etc.) a natural raw material (limestone, etc.) containing CaCO ₃ as a main component. Further, "light calcium carbonate" means calcium carbonate prepared by a synthetic method (chemical precipitation reaction, etc.).

Among calcium carbonate particles, heavy calcium carbonate particles are preferable because they have more contact interfaces with the thermoplastic resin and tend to improve the mechanical properties of the laminated sheet. Further, it is more preferable that the calcium carbonate particles contained in the inner layer are composed of heavy calcium carbonate particles, since the mechanical properties of the laminated sheet can be more easily improved.

The average particle size of the heavy calcium carbonate particles is preferably 0.7 μm or more and 6.0 μm or less, more preferably 1.0 μm or more and 5.0 μm or less, still more preferably 1.5 μm or more and 3.0 μm or less. In addition, it is preferable that particles having a particle size of 45 μm or more are not included in the particle size distribution of the heavy calcium carbonate particles.

When the average particle size of the heavy calcium carbonate particles is within the above range, the dispersibility in the inner layer is good, and an excessive increase in viscosity during production of the laminated sheet can be prevented. In addition, when the average particle size of the heavy calcium carbonate particles is within the above range, the heavy calcium carbonate particles are less likely to protrude from the inner layer or the surface of the laminated sheet and fall off, or to impair the appearance, mechanical strength, etc. , the effect of the present invention can be exhibited more easily.

In the present invention, the average particle size of the inorganic filler such as calcium carbonate particles is a value calculated from the results of measuring the specific surface area by an air permeation method according to JIS M-8511. As a measuring device, for example, a specific surface area measuring device SS-100 manufactured by Shimadzu Corporation can be preferably used.

The irregularity of the heavy calcium carbonate particles can be represented by the degree of spheroidization of the shape, that is, the degree of circularity. A lower roundness means a higher irregularity. The circularity of the heavy calcium carbonate particles is preferably 0.50 or more and 0.95 or less, more preferably 0.55 or more and 0.93 or less, and still more preferably 0.60 or more and 0.90 or less.

In the present invention, the term “roundness” refers to a value obtained by dividing the projected area of a particle by the area of a circle having the same perimeter as the projected perimeter of the particle ((projected area of the particle)/(projected perimeter of the particle). means the area of a circle with the same perimeter)). The method of measuring the roundness is not particularly limited. For example, the roundness can be specified by analyzing a projected image of particles obtained with a scanning microscope, a stereomicroscope, or the like, using commercially available image analysis software. Specifically, the projected area of the particle (A), the area of the circle having the same perimeter as the projected perimeter of the particle (B), the radius of the circle having the same perimeter as the projected perimeter of the particle (r), the particle can be calculated by the following formula based on the measurement results of the projection perimeter (PM) of the .
"Roundness" = A/B = A/πr ² = A x 4π/(PM) ²

As the pulverization method in the method for producing heavy calcium carbonate, either wet pulverization or dry pulverization can be used. Dry pulverization, which does not require a dehydration step, a drying step, or the like, is preferably used from an economical point of view. The pulverizer used for pulverizing the heavy calcium carbonate is not particularly limited, and examples thereof include impact pulverizers, pulverizers using pulverizing media such as ball mills, and roller mills. Conventionally known means such as air classification, wet cyclone, and decanter can be used as classification means in the method for producing heavy calcium carbonate.

Heavy calcium carbonate contains particles with a wide range of particle sizes, and is generally known to be poor in moldability. However, according to the present invention, since calcium carbonate particles such as ground calcium carbonate are surface-treated with a specific surface treatment agent, even a laminated sheet containing ground calcium carbonate in the inner layer has moldability. is good and the appearance can be excellent.

The inorganic filler used in the inner layer contains calcium carbonate particles, usually 90% by mass to 100% by mass, preferably 95% by mass to 100% by mass, more preferably substantially the entire amount excluding unavoidable impurities. . As will be described later, the calcium carbonate particles of the present invention are surface-treated with a specific surface treatment agent to enhance the dispersibility and reactivity of the calcium carbonate particles in the thermoplastic resin. When the content of the calcium carbonate particles in the inorganic filler is within the above range, the dispersibility of the inorganic filler in the thermoplastic resin is good and the elution from the resin composition is less likely to occur, which is preferable.

The content of calcium carbonate particles in the inner layer is 40.0% by mass or more and 80.0% by mass or less. Here, "content ratio of calcium carbonate particles in the inner layer" means "content ratio (% by mass) of calcium carbonate particles in 100% by mass of the inner layer". It is preferable from the viewpoint of environmental protection that the content of calcium carbonate particles in the inner layer is within the above range.

[surface treatment]
The calcium carbonate particles are surface treated with a surface treatment agent containing at least one of sulfonic acid and its salts , or a phosphate ester. That is, at least the calcium carbonate particles among the inorganic fillers used in the inner layer are surface-treated with the surface treating agent. When the calcium carbonate particles are surface-treated with the above surface treatment agent, the dispersibility and reactivity of the calcium carbonate particles in the thermoplastic resin are enhanced, thereby improving the physical properties and moldability of the resin composition constituting the inner layer. can do.

Calcium carbonate particles surface-treated with a conventional general-purpose surface-treating agent such as a fatty acid deteriorate in mechanical properties, physical properties such as elution under acidic conditions, etc., when they are highly filled in a thermoplastic resin. Cheap. On the other hand, the calcium carbonate particles surface-treated with the surface-treating agent of the present invention are resins with well-balanced physical properties such as mechanical properties and elution under acidic conditions even when highly filled in thermoplastic resins. A composition is obtained. Therefore, the inner layer containing the surface-treated calcium carbonate particles of the present invention is suitable for food packaging containers and tableware.

In addition, in the present invention, the inorganic filler other than the calcium carbonate particles may be surface-treated with the surface treating agent. In this case, the dispersibility and reactivity of the inorganic filler other than the calcium carbonate particles are enhanced, which may improve the physical properties and moldability of the resin composition forming the inner layer.

(Surface treatment agent containing sulfonic acid and its salt)
In the present invention, "a surface treatment agent containing at least one sulfonic acid and a salt thereof" is a concept including all "surface treatment agents containing at least one organic substance having a sulfonic acid group and a salt thereof". Hereinafter, "a surface treating agent containing at least one of sulfonic acid and its salt" is also referred to as a "sulfonic acid-based surface treating agent".

Examples of sulfonic acid-based surface treatment agents include, but are not limited to, methanesulfonic acid, ethanesulfonic acid, propane-1-sulfonic acid, propane-2-sulfonic acid, n-butane-1-sulfonic acid, and n-butane. -2-sulfonic acid, t-butane-2-sulfonic acid, 2-methyl-propane-1-sulfonic acid, n-octane-1-sulfonic acid, n-octane-2-sulfonic acid, n-dodecane-1- Sulfonic acid, pentadecanesulfonic acid, hexadecanesulfonic acid, octadecanesulfonic acid, dialkylsulfosuccinate, perfluorobutanesulfonic acid, alkylsulfonic acids such as perfluorooctane sulfonic acid; benzenesulfonic acid, p-toluenesulfonic acid, m-toluene Sulfonic acid, o-toluenesulfonic acid, various xylenesulfonic acids, cumenesulfonic acid, other arylsulfonic acids such as alkylbenzenesulfonic acid, naphthalenesulfonic acid, naphthalenesulfonic acid, naphthalenetrisulfonic acid, and alkylnaphthalenesulfonic acid; , laureth sulfuric acid, polyoxyethylene alkylphenol sulfonic acid, etc., and one or more of these and salts thereof. Here, as the salt, for example, alkali metal salts such as sodium and potassium, ammonium salts, and one or more of these are used.

Among sulfonic acid-based surface treatment agents, one or more sulfonic acids selected from the group consisting of alkylsulfonic acids, alkylbenzenesulfonic acids having an alkyl group having 2 or more carbon atoms, toluenesulfonic acid, and xylenesulfonic acid, and these is preferred. By surface-treating the calcium carbonate particles with these surface-treating agents, the amount of elution of the resin composition under acidic conditions can be further reduced.

Among the sulfonic acid-based surface treatment agents, alkylsulfonic acids, alkylbenzenesulfonic acids having an alkyl group of 2 or more carbon atoms, and salts thereof are more preferable. In general, the longer the alkyl chain length, the better the compatibility with the thermoplastic resin. can be further reduced.

Among the sulfonic acid-based surface treatment agents, alkylbenzene sulfonic acids having alkyl groups of 6 to 30 carbon atoms and/or 3 to 30 carbon atoms and salts thereof are more preferable. Among the sulfonic acid-based surface treatment agents, alkylsulfonic acids having 8 to 20 carbon atoms and/or alkylbenzenesulfonic acids having an alkyl group having 6 to 20 carbon atoms are particularly preferred. When the calcium carbonate particles are surface-treated with these surface-treating agents, the elution amount of the resin composition under acidic conditions can be significantly reduced.

Among sulfonic acid surface treatment agents, octylbenzenesulfonic acid, nonylbenzenesulfonic acid, decylbenzenesulfonic acid, dodecylbenzenesulfonic acid (laurylbenzenesulfonic acid), tetradecylbenzenesulfonic acid (myristylbenzenesulfonic acid), hexadecylbenzene Alkylbenzenesulfonic acids having an alkyl group of 8 to 18 carbon atoms such as sulfonic acid (palmitylbenzenesulfonic acid), octadecylbenzenesulfonic acid (stearylbenzenesulfonic acid), and salts thereof are more particularly preferred. When the calcium carbonate particles are surface-treated with these surface-treating agents, the elution amount of the resin composition under acidic conditions can be significantly reduced.

In the surface treatment agent, the number of alkyl groups on the benzene ring is not particularly limited, and may be the monoalkyl-substituted benzenesulfonic acid or the di- or trialkyl-substituted benzenesulfonic acid. . In addition, the alkyl group may be linear or branched, and may partially have a cyclic structure.

(Surface treatment method with sulfonic acid-based surface treatment agent)
There is no particular limitation on the surface treatment method of the calcium carbonate particles with the sulfonic acid-based surface treatment agent, and various known surface treatment methods can be used. For example, a method of adding sulfonic acid and its salt to a slurry of calcium carbonate particles and stirring (wet method), putting calcium carbonate particles and sulfonic acid and its salt into a grinder or mixer, and optionally heating and stirring. Examples include a method (dry method), and a method in which a hydrous cake of calcium carbonate and sulfonic acid are stirred while being heated in a mixer, but are not limited to these. Although depending on the type of sulfonic acid and its salt used as the surface treatment agent, it is generally preferable to carry out the surface treatment of light calcium carbonate by a wet method and the surface treatment of heavy calcium carbonate particles by a dry method.

The amount ratio of the sulfonic acid and its salt to the calcium carbonate particles in the surface treatment is not particularly limited. 10 parts by mass, more preferably 0.5 to 5 parts by mass, more preferably 1 to 3 parts by mass. With the amount of the sulfonic acid and its salt, uniform modification of the surface of the calcium carbonate particles is facilitated, and the risk of excessive sulfonic acid and its salt being eluted during use can be reduced. The amount of sulfonic acid on the surface of calcium carbonate particles can be quantified by a known analysis method such as solvent extraction or pyrolysis GC/MS.

When surface treatment is performed by a wet method, the concentration of calcium carbonate in the slurry and the type of solvent are not particularly limited, but the aqueous slurry preferably has a calcium carbonate concentration of about 10 to 300 g/L, more preferably about 25 to 200 g/L. . With the above concentration, even if the productivity of the surface treatment is enhanced, the viscosity is not increased and the workability is not deteriorated.

Moreover, when an aqueous solvent is used in the wet method, the surface treatment can be performed simply and at low cost, and safety can be maintained even if the treatment temperature is raised. The slurry temperature in the wet method is preferably 20 to 98°C, more preferably 40 to 90°C, still more preferably 60 to 80°C. By carrying out the surface treatment at 20° C. or higher, the surface treatment agent can be uniformly adsorbed and bonded onto the calcium carbonate particles, making it possible to perform the surface treatment uniformly. When the slurry temperature is set to 98° C. or lower, there is no risk of bumping or the like, so a pressure-resistant device can be dispensed with. Moreover, in the surface treatment by the wet method, the slurry may contain a surfactant.

Surface treatment by a dry method is carried out by kneading calcium carbonate particles with sulfonic acid and its salt in a kneader such as a Henschel mixer, a kneader, or an extrusion kneader. When heavy calcium carbonate particles are used as the calcium carbonate particles, a desired sulfonic acid and its salt may be added to the grinder to adjust the particle size of the calcium carbonate particles and simultaneously perform surface treatment.

The temperature during the surface treatment by the dry method can be arbitrarily set according to the type of sulfonic acid and its salt to be used. degree. By carrying out the surface treatment at 20° C. or higher, the surface treatment agent can be uniformly adsorbed and bonded onto the calcium carbonate particles, and the surface treatment can be performed uniformly. When the treatment temperature is about 150° C. or lower, the risk of thermal deterioration and deterioration of the surface treatment agent can be reduced. Further, the temperature during surface treatment by a dry method is more preferably a temperature above the melting point of the sulfonic acid and its salt used. This makes it easier for the surface treatment agent to more uniformly adsorb and bond onto the calcium carbonate particles. For example, surface treatment using a substance that is liquid at room temperature, such as laurylbenzenesulfonic acid, can be performed at room temperature. Surface treatment using p-toluenesulfonic acid allows kneading at a temperature of about 110 to 150°C. In the surface treatment of the dry method, a small amount of solvent may be used in combination as in the surface treatment of the wet method. For example, an aqueous solution of sulfonic acid and its salt may be added to the calcium carbonate particles and kneaded or pulverized. good.

Surface treatment using a hydrous cake of calcium carbonate particles can be performed under the same conditions as in the dry method, but the temperature during treatment is preferably 20 to 150°C, more preferably about 40 to 98°C. . This makes it possible to reduce the risk of uneven adsorption and bumping of the surface treatment agent in the surface treatment using the hydrous cake.

(Surface treatment agent containing phosphate ester)
In the present invention, "a surface treatment agent containing a phosphoric acid ester" is a concept that includes all surface treatment agents containing a phosphoric acid-based ester. Hereinafter, "a surface treatment agent containing a phosphate ester" is also referred to as a "phosphate ester-based surface treatment agent".

The phosphate-based surface treatment agent is not particularly limited as long as it contains a phosphoric acid-based ester. Examples include monoesters, diesters, and triesters of phosphoric acid and alcohol; Tri-ester; monoester, diester and triester of phosphoric acid and alkylphenol; monoester, diester and triester of phosphoric acid and alcohol and alkylene oxide; A surface treatment agent containing a phosphate ester having a structure in which is bonded, a phosphate ester having a structure having a carboxy group or a carbonyl group, one or more of these, and salts thereof is used. Here, as the salt, for example, alkali metal salts such as sodium and potassium, ammonium salts, and one or more of these are used. The phosphate ester-based surface treatment agent may be a surface treatment agent containing fatty acid, resin acid, fatty acid anhydride-modified resin, etc., in addition to the above phosphate ester, if necessary.

The phosphate ester contained in the phosphate ester-based surface treatment agent is preferably a monoester, a diester, a salt thereof, or a mixture of two or more thereof. In general, surface treatment agents containing monoesters and diesters are more effective in modifying the surface of calcium carbonate particles. Although the present invention is not bound by any particular theory, monoesters and diesters strongly react or adsorb to the surfaces of calcium carbonate particles via >P(=O)-O- groups in the molecules. it is conceivable that. In general, longer aliphatic hydrocarbon chains tend to have better compatibility with thermoplastic resins, and the effects of the present invention are particularly remarkable. For this reason, phosphoric acid esters having long-chain aliphatic hydrocarbon groups in the molecule, such as monoesters, diesters and triesters of phosphoric acid and long-chain alcohols; monoesters, diesters and tri-esters of phosphoric acid and long-chain alkylphenols; Esters; monoesters, diesters, triesters of phosphoric acid, long-chain alcohols and alkylene oxides; and salts thereof are preferred surface treatment agents comprising one or more phosphoric acid esters. The phosphate contained in the phosphate-based surface treatment agent is more preferably monoesters and diesters of phosphoric acid and long-chain alcohols, monoesters and diesters of phosphoric acid, long-chain alcohols and alkylene oxide, and their is one or more phosphate esters selected from salts of

The aliphatic hydrocarbon group in the phosphoric acid ester is not particularly limited. The aliphatic hydrocarbon groups in the phosphate ester include all saturated or unsaturated linear, branched, or cyclic aliphatic hydrocarbon groups. The aliphatic hydrocarbon group in the phosphoric acid ester may be substituted with a hydroxy group, an alkoxy group, an amino group, a nitro group, a cyano group, or the like. The types of substituents are not particularly limited, but for example, isopropyl group, butyl group, hexyl group, n-octyl group, isooctyl group, decyl group, dodecyl group (lauryl group), pentadecyl group (myristyl group), tetradecyl group (myristyl group), hexadecyl group (palmityl group), octadecyl group (stearyl group), hexadecenyl group (palmitoleyl group), octadecenyl group (oleyl group), octadecadienyl group (linoleyl group, elaidolinolenyl group), octadeca A trienyl group (linolenyl group), a hydroxyoctadecenyl group (linoleyl group), and the like are used. The number of carbon atoms in the aliphatic hydrocarbon group in the phosphoric acid ester is not particularly limited. can be a group hydrocarbon group.

In the present invention, the phosphoric acid ester is particularly preferably monoester, diester and/or salt thereof of phosphoric acid, alcohol and alkylene oxide. _{Such phosphate esters are} not _{particularly limited} . (In Formula 1, x, y, and z are integers of 1 or more; n and m are 1 or 2, and n+m=3). The hydrocarbon group (corresponding to C _x H _2x+1 ) of the phosphate ester may have, for example, an unsaturated bond or a cyclic structure, and the number of hydrogen atoms may be 2x-1 or less. may have a substituent of The phosphate ester can particularly effectively modify the surface of calcium carbonate particles, and it is possible to obtain a resin composition with a small amount of elution under acidic conditions and good physical properties such as mechanical strength. becomes. Although the present invention is not limited by any particular theory, having an alkylene oxide unit in the molecule spreads the aliphatic hydrocarbon group from the phosphoric acid ester on the surface of the calcium carbonate particles to a wider range, and as a result, It is considered that the compatibility between the surface-treated calcium carbonate particles and the thermoplastic resin is good.

Although there is no particular limitation on the number of carbon atoms in the aliphatic hydrocarbon group of the phosphate ester (eg, x in the above formula 1), it is preferably a phosphate ester having 3 to 20 carbon atoms or a salt thereof, more preferably 8 to 8 carbon atoms. C.18 phosphoric acid esters and salts thereof, more preferably C.sub.10-14 phosphoric acid esters and salts thereof, particularly preferably polyoxyethylene lauryl ether phosphoric acid and salts thereof are used.

Although the type of alkylene oxide is not particularly limited, ethylene oxide, propylene oxide, and butylene oxide are used, and ethylene oxide (y=2 in the above formula 1) is preferably used. The number of alkylene oxide units (z in formula 1) is also not particularly limited, but for example, 1 to 12, preferably 1 to 4 alkylene oxide units are present between each of the above aliphatic hydrocarbon groups and the phosphorus atom. to have

As the phosphate ester-based surface treatment agent, polyoxyethylene (1-4) lauryl ether phosphate and/or salts thereof are more preferably used, and more preferably monopolyoxyethylene (2) lauryl ether phosphate, di One or more phosphate esters selected from polyoxyethylene (2) lauryl ether phosphate and salts thereof are used.

(Surface treatment method with phosphate ester surface treatment agent)
There is no particular limitation on the surface treatment method of the calcium carbonate particles with the phosphate ester, and various known surface treatment methods can be used. For example, a method of adding a phosphate ester to a slurry of calcium carbonate particles and stirring (wet method), a method of adding calcium carbonate particles and a phosphate ester to a grinder or a mixer, and optionally heating and stirring (dry method). ), and a method in which a hydrous cake of calcium carbonate particles and a phosphoric acid ester are stirred while being heated in a mixer, but are not limited thereto. Depending on the type of phosphate ester used as the surface treatment agent, it is generally preferred that the surface treatment of the light calcium carbonate particles is performed by a wet method, and the surface treatment of the heavy calcium carbonate particles is performed by a dry method.

The amount ratio of the phosphate ester to the calcium carbonate particles during the surface treatment is not particularly limited. , more preferably 0.5 to 5 parts by mass, more preferably about 1 to 3 parts by mass. With the above amount of phosphate, uniform modification of the surface of the calcium carbonate particles is facilitated, and the risk of excess phosphate eluting during use can be reduced. The amount of phosphate on the surface of the calcium carbonate particles can be quantified by a known analysis method such as solvent extraction or pyrolysis GC/MS.

In the case of surface treatment by a wet method, there are no particular restrictions on the concentration of calcium carbonate particles in the slurry and the type of solvent. Preferably, the aqueous slurry has a calcium carbonate particle concentration of 10 to 300 g/L, particularly 25 to 200 g/L. With the above concentration, even if the productivity of the surface treatment is enhanced, the viscosity is not increased and the workability is not deteriorated.

Moreover, when an aqueous solvent is used in the wet method, the surface treatment can be performed simply and at low cost, and safety can be maintained even if the treatment temperature is raised. The slurry temperature in the wet method is preferably 20 to 98°C, more preferably 40 to 90°C, still more preferably 60 to 80°C. By carrying out the surface treatment at 20° C. or higher, the surface treatment agent can be uniformly adsorbed and bonded onto the calcium carbonate particles, making it possible to perform the surface treatment uniformly. When the slurry temperature is set to 98° C. or lower, there is no risk of bumping or the like, so a pressure-resistant device can be dispensed with. Moreover, in the surface treatment by the wet method, the slurry may contain a surfactant.

Surface treatment by a dry method can be performed by kneading calcium carbonate particles and a phosphate ester in a kneader such as a Henschel mixer, a kneader, or an extrusion kneader. When heavy calcium carbonate particles are used as the calcium carbonate particles, a desired phosphoric acid ester may be added to the grinder to adjust the particle size of the calcium carbonate particles and simultaneously perform surface treatment.

The temperature during the surface treatment by the dry method can be arbitrarily set according to the type of phosphoric acid ester to be used. do. By carrying out the surface treatment at 20° C. or higher, the surface treatment agent can be uniformly adsorbed and bonded onto the calcium carbonate particles, and the surface treatment can be performed uniformly. When the treatment temperature is about 150° C. or lower, the risk of thermal deterioration and deterioration of the surface treatment agent can be reduced. Further, the temperature during the surface treatment by the dry method is more preferably set to a temperature equal to or higher than the melting point of the phosphoric acid ester used. This makes it easier for the surface treatment agent to more uniformly adsorb and bond onto the calcium carbonate particles. For example, surface treatment using a substance that is liquid at room temperature, such as polyoxyethylene lauryl ether phosphate, can be performed at room temperature. Surface treatment using polyoxyethylene stearyl ether phosphoric acid or the like can be kneaded at a temperature of about 50 to 150°C. In the surface treatment of the dry method, a small amount of solvent may be used in combination in the same manner as the surface treatment of the wet method. It may be kneaded or pulverized.

Surface treatment using a hydrous cake of calcium carbonate particles can be performed under the same conditions as in the dry method, but the temperature during treatment is preferably 20 to 150°C, more preferably about 40 to 98°C. This makes it possible to reduce the risk of uneven adsorption and bumping of the surface treatment agent in the surface treatment using the hydrous cake.

<Thermoplastic resin>
As the thermoplastic resin used in the inner layer, any resin that can be usually blended in the resin sheet can be used. A thermoplastic resin can be used individually by 1 type or in combination of 2 or more types.

As thermoplastic resins, for example, polyolefin resins, polyester resins, polystyrene resins, etc. are used. Among these, polyolefin-based resins are preferable from the viewpoint of moldability and the like.

In the present invention, "polyolefin-based resin" means a polyolefin-based resin having olefin component units as a main component. The phrase “mainly composed of olefin component units” means that the olefin component unit is 50% by mass or more (preferably 75% by mass or more, more preferably 85% by mass or more, and still more preferably 90% by mass or more) in the polyolefin resin. meant to be included. The method for producing the polyolefin resin used in the present invention is not particularly limited, and any method using a Ziegler-Natta catalyst, a metallocene catalyst, a radical initiator (oxygen, peroxide, etc.) or the like may be used. .

Polyolefin-based resins include, for example, polypropylene-based resins and polyethylene-based resins.
The thermoplastic resin is preferably a resin containing a polypropylene-based resin and/or a polyethylene-based resin, more preferably a resin from the viewpoint of easily realizing a good appearance and more easily suppressing non-uniformity in mechanical properties. is a polypropylene-based resin and/or a polyethylene-based resin.

[Polypropylene resin]
The polypropylene resin in the present invention preferably contains 50 mass % or more, more preferably 60 mass % or more, still more preferably 70 mass % or more, and particularly preferably 80 mass % or more of the propylene component unit.

Polypropylene homopolymers (propylene homopolymers), copolymers of propylene and other α-olefins (those copolymerizable with propylene), and the like are used as polypropylene resins.
"Other α-olefins" include, for example, α-olefins having 4 to 10 carbon atoms (ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4- dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, etc.) are used.

As the propylene homopolymer, linear or branched polypropylene or the like showing various stereoregularities (isotactic, syndiotactic, atactic, hemiisotactic, etc.) is used.

The propylene copolymer may be a polypropylene random copolymer (random copolymer), a polypropylene block copolymer (block copolymer), a binary copolymer, a terpolymer, or the like. Specifically, ethylene-propylene random copolymers, butene-1-propylene random copolymers, ethylene-butene-1-propylene random terpolymers, ethylene-propylene block copolymers and the like are used.

As the polypropylene-based resin, a resin containing a polypropylene homopolymer and/or a polypropylene block polymer is preferably used, and a resin that is a polypropylene homopolymer and/or a polypropylene block polymer is more preferably used.

[Polyethylene resin]
The polyethylene-based resin in the present invention contains a resin having an ethylene component unit of preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and particularly preferably 80% by mass or more.

Polyethylene-based resins include high-density polyethylene (HDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), ethylene-vinyl acetate copolymer, ethylene-propylene copolymer. Copolymer, ethylene-propylene-butene 1-copolymer, ethylene-butene 1-copolymer, ethylene-hexene 1-copolymer, ethylene-4-methylpentene 1-copolymer, ethylene-octene 1-copolymer and the like are used.

As the polyethylene-based resin, a resin containing high-density polyethylene and linear low-density polyethylene, more preferably a resin containing only high-density polyethylene and linear low-density polyethylene is used.

The high-density polyethylene, MFR (190 ° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) in high-density polyethylene is preferably 5 g / 10 minutes or more and 15 g / 10 minutes or less, more preferably 7 g /10 min or more and 13 g/10 min or less is used.

As linear low-density polyethylene, MFR (190 ° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) in linear low-density polyethylene is preferably 0.5 g / 10 minutes or more and 1.5 g / 10 minutes or less, more preferably 0.7 g/10 minutes or more and 1.3 g/10 minutes or less.

In resins containing high-density polyethylene and linear low-density polyethylene, the mass ratio of both (high-density polyethylene:linear low-density polyethylene) is preferably 90:10 to 50:50, more preferably 92:8 to 50:50, more preferably 94:6 to 50:50.

In a preferred embodiment of the present invention, the polyethylene-based resin includes high-density polyethylene and linear low-density polyethylene,
MFR (190° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) in high-density polyethylene is 5 g/10 minutes or more and 15 g/10 minutes or less,
MFR (190 ° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) in linear low density polyethylene is 0.5 g / 10 minutes or more and 1.5 g / 10 minutes or less,
The mass ratio of high density polyethylene to linear low density polyethylene is 90:10 to 50:50.

<Proportion of calcium carbonate particles blended in the inner layer>

The lower limit of the content of calcium carbonate particles contained in the inner layer (total amount of calcium carbonate particles) is 40.0% by mass or more relative to the inner layer. is preferably 42.0% by mass or more, more preferably 44.0% by mass or more.

The upper limit of the content of calcium carbonate particles contained in the inner layer (the total amount of calcium carbonate particles) is 80.0% by mass or less with respect to the inner layer. From the viewpoint of facilitating suppression of uneven distribution of particles, the content of the inner layer is 80.0% by mass or less, preferably 75.0% by mass or less, and more preferably 70.0% by mass or less.

The mass ratio of the first calcium carbonate particle group to the second calcium carbonate particle group (first calcium carbonate particle group: second calcium carbonate particle group) in the inner layer is 99.95:0.05 to 99.99:0.01.
The mass ratio (first calcium carbonate particle group: second calcium carbonate particle group) is preferably 99.96:0.04 to 99.99:0.01, more preferably 99.97:0.03 to 99.99:0.01.

<Proportion of thermoplastic resin blended in inner layer>
The proportion of the thermoplastic resin blended in the inner layer is not particularly limited as long as it is within the range where a sufficient amount of the inorganic filler can be blended.

The lower limit of the thermoplastic resin content is preferably 20.0% by mass or more, more preferably 22.0% by mass or more, and still more preferably 24.0% by mass or more with respect to the inner layer.

The upper limit of the thermoplastic resin content is preferably 60.0% by mass or less, more preferably 58.0% by mass or less, and even more preferably 56.0% by mass or less with respect to the inner layer.

<Other components blended in the inner layer>
If necessary, the inner layer may contain other components other than the inorganic filler and the thermoplastic resin as long as the effects of the present invention are not impaired.

As other components, arbitrary components that can be usually blended in the resin sheet can be used.
Other components include, for example, lubricants, dispersants, antistatic agents, antioxidants, heat stabilizers, ultraviolet absorbers, and the like.
The types and amounts of these components can be appropriately set according to the effects to be obtained.

(2) Outer layer The outer layer is a pair of layers laminated on the front and back surfaces of the inner layer. That is, in the laminated sheet of the present invention, two outer layers are formed so as to sandwich the inner layer. In the present invention, the pair of layers is also referred to as a first outer layer and a second outer layer.

The configurations of the first outer layer and the second outer layer may be the same or different. However, the first outer layer and the second outer layer each contain a thermoplastic resin.

Preferred embodiments of the present invention include embodiments in which the configurations (composition, thickness, shape, etc.) of the first outer layer and the second outer layer are all the same.

<Thermoplastic resin>
As the thermoplastic resin used in the outer layer, any resin that can be usually blended in the resin sheet can be used. A thermoplastic resin can be used individually by 1 type or in combination of 2 or more types.

As the thermoplastic resin used for the outer layer, the same thermoplastic resin as used for the inner layer can be used. In addition, in the laminated sheet of the present invention, the thermoplastic resin used for the outer layer and the thermoplastic resin used for the inner layer may be the same or different.

Preferred aspects of the present invention include all of the following aspects.
(Mode 1) The thermoplastic resin blended in the outer layer and the thermoplastic resin blended in the inner layer are all the same. (Mode 2) The thermoplastic resin blended in the first outer layer and the second outer layer. Aspect (Aspect 3) in which the thermoplastic resin blended in and the thermoplastic resin blended in the inner layer are all different (Aspect 3) The thermoplastic resin blended in the first outer layer, the thermoplastic resin blended in the second outer layer, and an aspect in which only two of the thermoplastic resins blended in the inner layer are the same

Of the above modes, mode 3 is preferable from the viewpoint that the effects of the present invention are likely to be exhibited.

In the above (mode 3), from the viewpoint that the effect of the present invention is likely to be exhibited, the mode in which the thermoplastic resin blended in the first outer layer and the thermoplastic resin blended in the second outer layer are the same, i.e. A preferred embodiment is that only the thermoplastic resin blended in the inner layer is different.

The thermoplastic resins in the first outer layer and the second outer layer are preferably resins containing polypropylene-based resins and/or polyethylene-based resins, and more preferably polypropylene-based resins and/or polyethylene-based resins. Resin is used.

<Proportion of thermoplastic resin blended in outer layer>
The proportion of the thermoplastic resin blended in the outer layer is not particularly limited as long as the resin sheet can be molded.

The lower limit of the thermoplastic resin content is preferably 80.0% by mass or more, more preferably 90.0% by mass or more, and still more preferably 99.0% by mass or more, relative to the outer layer.

The content of the thermoplastic resin is preferably 100.0% by mass with respect to the outer layer.

<Other components blended in the outer layer>
If necessary, other components than the thermoplastic resin may be added to the outer layer as long as the effects of the present invention are not impaired.

As other components, arbitrary components that can be usually blended in the resin sheet can be used.
Such ingredients include inorganic fillers (calcium carbonate, clay, kaolin, mica, calcium sulfate, barium sulfate, zinc oxide, silica, talc, titanium dioxide, silicon dioxide, bentonite, etc.), lubricants, dispersants, electrostatic Inhibitors, antioxidants, heat stabilizers, ultraviolet absorbers and the like are used.
The types and amounts of these components can be appropriately set according to the effects to be obtained.

A preferred embodiment of the present invention includes a laminated sheet in which the outer layer is made of thermoplastic resin only.

(3) Thickness of each layer of the laminated sheet, etc. In the laminated sheet of the present invention, the ratio of the thicknesses of the outer layers constituting the pair of outer layers, that is, the ratio of the thicknesses of the first outer layer and the second outer layer They are respectively 2.0% or more and 20.0% or less with respect to the total thickness of the sheet. Therefore, in the laminated sheet of the present invention, the total thickness of the outer layers, that is, the total thickness of the first outer layer and the second outer layer, is 4.0% or more of the total thickness of the laminated sheet. 0% or less.
In the laminated sheet of the present invention, by making the thickness of the outer layer thinner than the thickness of the inner layer, it is possible to exhibit excellent mechanical properties exhibited by the inner layer while exhibiting a good appearance. It has become.

The lower limit of the thickness ratio of the first outer layer and the second outer layer is 2.0% or more, preferably 2.5, relative to the total thickness of the laminated sheet, from the viewpoint that the appearance tends to be good. % or more, more preferably 3.0% or more, and still more preferably 4.0% or more.

The upper limit of the thickness ratio of the first outer layer and the second outer layer is 20.0% or less, preferably 18%, relative to the total thickness of the laminated sheet, from the viewpoint that the effect of the inner layer is likely to be exhibited. 0% or less, more preferably 16.0% or less, still more preferably 10.0% or less, and particularly preferably 6.0% or less.

In the laminate sheet of the present invention, the thickness ratio of the inner layer is adjusted according to the thickness of the outer layer, and is 60.0% or more and 96.0% or less of the total thickness of the laminate sheet.

The lower limits of the thicknesses of the first outer layer and the second outer layer are preferably 5.0 μm or more, more preferably 10.0 μm or more, from the viewpoint of easily obtaining a good appearance.

The upper limits of the thicknesses of the first outer layer and the second outer layer are preferably 50.0 μm or less, more preferably 45.0 μm or less, respectively, from the viewpoint of moldability and the like.

The lower limit of the thickness of the inner layer is preferably 50.0 μm or more, more preferably 100.0 μm or more, from the viewpoint of easily obtaining good mechanical properties.

The upper limit of the thickness of the inner layer is preferably 950.0 μm or less, more preferably 900.0 μm or less, from the viewpoint of moldability and the like.

The lower limit of the total thickness of the laminated sheet is adjusted according to the thickness of the outer layer and the inner layer, preferably 100.0 μm or more, more preferably 150.0 μm or more.

The upper limit of the total thickness of the laminated sheet is adjusted according to the thickness of the outer layer and the inner layer, preferably 990.0 μm or less, more preferably 700.0 μm or less.

The density of the laminated sheet is not particularly limited.

(4) Planar Occupancy of Exposed Area of Inorganic Filler on End Faces of Inner Layer The laminated sheet of the present invention usually has end faces. The end face of the laminated sheet is usually formed by laminating the end faces of the outer layer and the inner layer. The end face of the laminated sheet is, for example, a manufacturing end face formed when the laminated sheet is manufactured, a cut surface formed when cutting a manufactured laminated sheet having a large area, or the like. Laminated sheets are often used by cutting a produced laminated sheet having a large area into a desired size. For this reason, many of the laminate sheets used have cut surfaces that are end surfaces.

The inner layer of the laminated sheet contains an inorganic filler and a thermoplastic resin, and usually the inorganic filler is dispersed in the thermoplastic resin.
In addition, voids may occur in the inner layer of the laminated sheet due to stretching during manufacturing, etc. It is presumed that voids are generated by peeling at the interface between the inorganic filler and the thermoplastic resin during stretching. . Therefore, when the end face of the laminated sheet is the cut surface, the thermoplastic resin, the inorganic filler and the voids are usually exposed on the end face of the inner layer.

In the laminated sheet of the present invention, the measured plane occupancy MPO of the inorganic filler in at least one cut surface of the inner layer is the theoretical plane occupancy of the inorganic filler in the cut surface calculated based on the content of the inorganic filler in the inner layer. It is lower than TPO by 2% or more.

Here, the measured plane occupancy MPO, the theoretical plane occupancy TPO, and the meaning of defining the difference between them will be described.

In the actual cutting surface MCU of the inner layer, the plastic resin may be plastically deformed by the shearing force. Therefore, in the actual cut surface MCU of the inner layer, at least part of the surface of the inorganic filler such as calcium carbonate particles may be covered with plastically deformed plastic resin.

<Measured Plane Occupancy MPO>
The measured plane occupancy MPO is the plane occupancy of the inorganic filler actually measured on the actual cut surface MCU of the inner layer. The actual cut surface MCU of the inner layer is divided into two aspects: the plastic resin is not plastically deformed and the surface of the inorganic filler is not covered with the plastic resin, and the plastic resin is plastically deformed and the surface of the inorganic filler is covered with the plastic resin. , including two aspects.

For example, in the actual cut surface MCU of the inner layer, S _MT is the total area, S MRN is the exposed area of the plastic resin that does not cover the surface of the inorganic filler in the exposed area of the plastic resin, and S _MRN is the exposed area of the plastic resin that does not cover the surface of the inorganic filler in the exposed area of the plastic resin. _{S MRC} is the _exposed area of the plastic resin covering the surface of the agent, S _MF is the exposed area of the inorganic _filler , and S _MV is the area occupied by the _{voids .} . The measured plane occupancy MPO is calculated by S _MF /S _MT . In addition, _SMRC becomes 0 in the aspect in which the plastic resin is not plastically deformed and the surface of the inorganic filler is not covered with the plastic resin.

The measured plane occupancy MPO can be calculated, for example, from an image observed with an electron microscope. For example, select arbitrary 4 sections on the same plane in the cross section so that the area per section is 0.014 mm ² , measure the area occupied by the inorganic filler with respect to the area of each section, and The average occupancy can be calculated as an average. Note that one or more arbitrary partitions should not overlap each other in position. Any one or more sections are not particularly limited as long as they are located on one end surface of the cut sheet, but each section is preferably adjacent to at least one other section. Here, the term “adjacent” refers to a distance between points of closest approach of each section that is at least 0.1 mm or less, preferably at least 0.09 mm or less, and more preferably 0.07 mm or less. , more preferably within 0.04 mm, and even more preferably within 0.01 mm. Also, any one or more partitions may be of any shape, such as a quadrangle (square, rectangle, etc.), circle, or the like.

<Theoretical Plane Occupancy TPO>
On the other hand, theoretically, the plane occupancy TPO is the plane occupancy of the inorganic filler in the ideal cut surface ICU of the inner layer, assuming that the plastic resin does not deform plastically and the surface of the inorganic filler is not covered with the plastic resin. .

The theoretical plane coverage TPO is calculated from, for example, the density (specific gravity) of the inner layer, the content ratio (CR) of the inorganic filler with respect to the entire inner layer, and the density (specific gravity) of the inorganic filler.

An example of a specific calculation method of the theoretical plane occupation ratio TPO is as follows. First, the density ratio RD is calculated from "the density (specific gravity) of the inner layer"/"the density (specific gravity) of the inorganic filler". Next, using the "density ratio RD" and the "mass ratio MR of the inorganic filler to the entire inner layer", the "space occupation ratio SO of the inorganic filler" is calculated. Furthermore, a virtual inner layer columnar body VIC having a uniform space occupation ratio SO in the height direction is created. Next, the plane occupancy TPOVB [%] of the inorganic filler on the bottom surface VB of the virtual inner layer columnar body VIC is defined as the theoretical plane occupancy TPO [%] of the inorganic filler on the cut surface.

In the laminated sheet of the present invention, the fact that the measured plane occupancy MPO is theoretically 2% or more lower than the plane occupancy TPO is due to the fact that a part of the surface of the inorganic filler such as calcium carbonate particles is coated with a thermoplastic resin that is plastically deformed at the time of cutting. It is thought that it is because Such a coating is preferable because it reduces sharp protrusions on the cut surface of the inner layer sheet and makes it difficult for the user's finger or the like handling the inner layer sheet or the laminated sheet to be cut. In addition, it is presumed that the coating coats the voids at the interface between the inorganic filler and the thermoplastic resin on the cut surface and imparts excellent water resistance to the laminated sheet.

The voids in the inner layer will be explained. The inner layer is usually obtained by melt-kneading a resin composition containing an inorganic filler and a thermoplastic resin and molding it into a sheet. In the obtained inner layer sheet, it is considered that peeling occurs at the interface between the inorganic filler and the thermoplastic resin when the sheet is stretched. It is thought that when the resin composition is stretched, the separation occurring at the interface propagates and expands, forming voids in the resin composition. In addition, when the voids appearing on the cut surface of the inner layer of the laminated sheet are independent voids, water absorption is difficult to progress, and when the voids are continuous voids, water absorption is likely to progress and water resistance is likely to be impaired. In the present invention, the fact that the actually measured plane occupancy MPO is theoretically lower than the plane occupancy TPO by 2% or more is considered to contribute to suppressing water absorption from the sheet edge surfaces and lowering the water absorption rate of the sheet. .

The measured plane occupation ratio MPO is not particularly limited as long as it is theoretically 2% or more lower than the plane occupation ratio TPO, but it is preferably 3% or more, more preferably 4% or more, and even more preferably 5% or more. As for the upper limit, theoretically, the actually measured plane occupancy MPO may be 20% or less (15% or less, 10% or less, etc.) from the plane occupancy TPO.

The number of cut surfaces of the inner layer in the laminated sheet is not particularly limited, and may be 3 or more (4, 5, 6, etc.). In addition, among the cut surfaces of the inner layer of the laminated sheet, the cut surfaces that are lower than the theoretical plane occupation ratio TPO of the measured plane occupation ratio MPO by 2% or more are preferably cut by 10% or more of the total number of cut surfaces. more preferably 25% or more of the number of cut surfaces, more preferably 50% or more of the number of cut surfaces, particularly preferably 75% or more of the number of cut surfaces, most preferably 100 It is on the cutting surface of the number of %.

(5) Method for producing laminated sheet The method for producing the laminated sheet of the present invention is not particularly limited, and conventionally known methods for producing multilayer sheets and laminates can be used.

As a method for producing the laminated sheet, for example, the following method is used.
・Method of laminating the inner layer and outer layer formed into a sheet with a calender roll ・Method of co-extrusion of the inner layer and the outer layer A method in which co-extrusion molding is performed in the same process A method by extrusion inflation method using multiple annular dies

The laminated sheet may be stretched as necessary.

(6) Uses of Laminated Sheet The laminated sheet of the present invention can be used for any application of ordinary resin sheets.

The method for forming the laminated sheet of the present invention is not particularly limited, and vacuum forming, air pressure forming, match mold forming and the like are used.
Among these, vacuum forming is preferable from the viewpoint of ease of forming. Therefore, the laminated sheet of the present invention includes an aspect that is a laminated sheet for vacuum forming.

A preferred application of the laminated sheet of the present invention is as a material for packaging containers.
Accordingly, the present invention includes packaging containers, particularly food packaging containers, formed from the laminated sheet of the invention.

Food packaging containers include arbitrary containers such as trays, cups, lids of various containers, and bags.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Preparation and Evaluation of Laminated Sheet>
A laminated sheet was produced by the following method and evaluated.

(1) Preparation of materials Materials for each layer were prepared as follows.

<Inorganic filler>
Heavy calcium carbonate particles-1: Heavy calcium carbonate particles (Softon (trade name) 1000 manufactured by Bihoku Funka Kogyo Co., Ltd., average particle size: 2.2 μm, specific surface area: 10000 cm ² /g, no surface treatment)

The average particle size of heavy calcium carbonate particles-1 is a value specified based on the air permeation method according to JIS M-8511.

<Surface treatment agent>
[Sulfonic acid-based surface treatment agent]
・ Sulfonic acid-based surface treatment agent-1: xylene sulfonic acid (Taika Tox (registered trademark) 110 manufactured by Tayka Co., Ltd., active ingredient 96.7%)
・ Sulfonic acid-based surface treatment agent-2: linear alkylbenzene sulfonic acid (Taika Power (registered trademark) L121 manufactured by Tayka Co., Ltd., active ingredient 96.7%)
・Sulfonic acid surface treatment agent -3: Sodium p-toluenesulfonate ・Sulfonic acid surface treatment agent -4: 1-Sodium dodecanesulfonate ・Sulfonic acid surface treatment agent -5: Sodium cumenesulfonate (Tayca Co., Ltd.) manufactured by Teikatox (registered trademark) N5040, active ingredient about 40%)

[Phosphate ester-based surface treatment agent]
· Phosphate ester surface treatment agent-1: Polyoxyethylene lauryl ether phosphoric acid (Toho Chemical Industry Co., Ltd. Phosphanol (registered trademark) ML-220: C ₁₂ H ₂₅ O (C ₂ H ₄ O) ₂ - Mixture of P(=O)(OH) ₂ and [C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₂ ] ₂ P(=O)OH, first acid number 140-160)
· Phosphate ester-based surface treatment agent-2: Polyoxyethylene laurylphenol phosphate (aromatic EO phosphate, Toho Chemical Industry Co., Ltd. Phosphanol (registered trademark) LF-200: C ₁₂ H ₂₅ C ₄ H mixtures of _{4O ( C2H4O} ) _{2 -} P(=O) ₍ OH) ₂ and [ _{C12H25OC4H4 ( C2H4O} ) ₂ ] _{2P (} =O)OH, First acid value 95-115)
· Phosphate ester-based surface treatment agent-3: Lauryl phosphoric acid (Toho Chemical Industry Co., Ltd. Phosphanol (registered trademark) ML-200: C ₁₂ H ₂₅ OP (= O) (OH) ₂ and (C ₁₂ H ₂₅ O) ₂ P(=O)OH, 1st acid number 190-210)
· Phosphate ester-based surface treatment agent-4: Sodium salt of phosphate ester having a long unsaturated aliphatic hydrocarbon chain and ethylene oxide unit (unsaturated EO phosphate ester salt, Phosphanol manufactured by Toho Chemical Industry Co., Ltd. (registered trademark) RD-720, hydrocarbon chain carbon number 18, ethylene oxide unit number 7)

[Other surface treatment agents]
- Surface treatment agent-C1: Maleic anhydride-modified polypropylene (maleic anhydride-modified resin; Umex (registered trademark) 1010 manufactured by Sanyo Chemical Industries, Ltd.)
・Surface treatment agent-C2: styrene/maleic acid ester (maleic acid-modified resin; Regit (registered trademark) SM-101 manufactured by Sanyo Chemical Industries, Ltd.)

<Surface-treated inorganic filler>
・Surface-treated heavy calcium carbonate particles-C1: Fatty acid surface-treated heavy calcium carbonate particles (average particle size 2.2 μm; Ryton (registered trademark) S-4 manufactured by Bihoku Funka Kogyo Co., Ltd.)

<Thermoplastic resin>
PP-1: polypropylene homopolymer (polypropylene homopolymer, Prime Polypro (registered trademark) E111G manufactured by Prime Polymer Co., Ltd., melting point 160 ° C.)
・ PP-2: polypropylene block copolymer (melting point 160 ° C.)
- Blend of PE:HDPE and LLDPE (HDPE:LLDPE (mass ratio) = 70:30)
The MFR (190° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) of the above HDPE is 7.5 g/10 minutes.
The MFR (190° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) of the above LLDPE is 0.8 g/10 minutes.

<Lubricant>
・Magnesium stearate lubricant

(2) Preparation of Laminated Sheet Using the materials shown in the table, a three-layered laminated sheet was prepared by the multi-layer T-die method.
The total thickness of the laminated sheet was set at 300.0 μm.
The thickness of the inner layer was set to 270 μm (90% of the total thickness of the laminated sheet).
An outer layer (a first outer layer and a second outer layer) was provided on both sides of the inner layer, and the thickness of each outer layer was set to 15 μm (5% of the total thickness of the laminated sheet).
The method of preparing the inner layer resin composition of each example and comparative example will be described later.

(3) Evaluation of laminated sheet Appearance and mechanical properties of the laminated sheet were evaluated by the following methods. The results are shown in the "evaluation" section of the table.

<Appearance>
The appearance of the molded article obtained from the laminated sheet was evaluated by the following method.

[Appearance evaluation method]
The laminated sheet was preheated with a far-infrared heater and then formed into a tray-shaped container having a bottom diameter of 50 mm, an opening diameter of 50 mm, a height of 30 mm and a flange width of 5 mm using a vacuum forming machine.
The appearance of the obtained container was visually observed and evaluated according to the following criteria.

[Appearance Evaluation Criteria]
A: The overall surface condition is very good (no unevenness, deformation, breakage, etc. occurred at all).
B: The overall surface condition is good (a little unevenness, deformation, or breakage occurred).
C: The overall surface condition is poor (unevenness, deformation, breakage, etc. clearly occurred).

<Mechanical properties>
The mechanical properties (tensile strength) of the laminated sheets were evaluated by the following methods.

[Method for evaluating mechanical properties]
The tensile strength of each laminated sheet was measured using Autograph AG-100kNXplus (Shimadzu Corporation) under conditions of 23° C. and 50% RH according to JIS K 7161-2:2014.
A sample (dumbbell shape) cut out from each laminated sheet was used as the test piece. The drawing speed was set at 50 mm/min.

[Evaluation Criteria for Mechanical Properties]
A: Tensile strength was 13 MPa or more.
B: The tensile strength was 10 MPa or more and less than 13 MPa.
C: Tensile strength was less than 10 MPa.

<Moldability>
The moldability of the laminated sheet was evaluated by the following method.

[Method for evaluating moldability]
Each molded container was visually observed and measured, and the ease of molding of each laminated sheet was evaluated according to the following criteria.

[Evaluation Criteria for Moldability]
A: Molded to almost the target dimensions, and no shape distortion was observed.
B: Some of the dimensions differed from the target values, but no shape distortion was visually observed.
C: Distortion of container shape was visually observed.

[Example A1]
(Preparation of resin composition for inner layer)
Heavy calcium carbonate particles having an average particle diameter of 2.2 μm (according to the air permeation method) and a specific surface area of 10,000 cm ² /g (Softon (trade name) 1000 manufactured by Bihoku Funka Kogyo Co., Ltd.; heavy calcium carbonate particles-1 ) was added to 100 parts by mass of xylene sulfonic acid (Taika Tox (registered trademark) 110 manufactured by Tayka Co., Ltd., active ingredient 96.7%; sulfonic acid-based surface treatment agent-1), together with 3 parts by mass, in a Henschel mixer at a temperature of 120. °C and a rotation speed of 1200 rpm for 30 minutes to carry out surface treatment.

60 parts by mass of the surface-treated calcium carbonate particles obtained above and 40 parts by mass of a polypropylene homopolymer (Prime Polypro (registered trademark) E111G manufactured by Prime Polymer Co., Ltd., melting point 160° C.) were mixed with 0.2 parts by mass of a magnesium stearate lubricant. Together with 5 parts by mass, it is put into a co-rotating twin-screw kneading extruder HK-25D (φ25 mm, L / D = 41) manufactured by Parker Corporation, extruded at a cylinder temperature of 190 to 200 ° C., cooled and cut. pelletized with

(Outer layer material)
A polypropylene homopolymer (polypropylene homopolymer, Prime Polypro (registered trademark) E111G manufactured by Prime Polymer Co., Ltd., melting point 160° C.; PP-1) was prepared.

Table 1 shows the test results.

[Comparative Example 1]
The same operation as in Example A1 was performed except that untreated SOFTON 1000 was used as the inorganic powder. Table 2 shows the test results.

[Example A2]
Instead of xylenesulfonic acid (xylenesulfonic acid sulfonic acid-based surface treatment agent-1), linear alkylbenzenesulfonic acid (Tayka Power (registered trademark) L121 manufactured by Tayka Corporation, active ingredient 96.7%; sulfonic acid-based surface treatment agent -2) was performed in the same manner as in Example A1. Table 1 shows the test results.

[Example A3]
SOFTON 1000 was dispersed in purified water (concentration 100 g/L) to prepare a slurry. To this slurry, 3 g of sodium p-toluenesulfonate (sulfonic acid-based surface treatment agent-3) was added to 1 L of slurry (3% by mass based on calcium carbonate particles), stirred at 50° C. for 30 minutes, and filtered. Separated and dried to obtain surface-treated calcium carbonate particles.
A sheet was prepared in the same manner as in Example A1 except that the surface-treated calcium carbonate particles were used, and the physical properties were evaluated. Table 1 shows the test results.

[Example A4]
The same operation as in Example A3 was performed except that sodium 1-dodecanesulfonate (sulfonic acid surface treatment agent-4) was used instead of sodium p-toluenesulfonate (sulfonic acid surface treatment agent -1). . Table 1 shows the test results.

[Comparative Example 2]
As the surface-treated calcium carbonate particles, commercially available fatty acid surface-treated heavy calcium carbonate particles (average particle size 2.2 μm; Ryton (registered trademark) S-4 manufactured by Bihoku Funka Kogyo Co., Ltd.; surface-treated heavy calcium carbonate particles-C1 ) was performed in the same manner as in Example A1 except that ) was used. Table 2 shows the test results.

[Comparative Example 3]
Maleic anhydride-modified polypropylene (maleic anhydride-modified resin; Umex (registered trademark) 1010 manufactured by Sanyo Chemical Industries, Ltd.; surface treatment agent-C1 instead of xylenesulfonic acid (sulfonic acid-based surface treatment agent-1) as a surface treatment agent ) was used, and the same operation as in Example A1 was performed except that the temperature during the surface treatment was 180°C. Table 2 shows the test results.

[Comparative Example 4]
The same operation as in Comparative Example 3 was performed except that styrene/maleic acid ester (maleic acid-modified resin; Regit (registered trademark) SM-101 manufactured by Sanyo Chemical Industries, Ltd.; surface treatment agent-C2) was used as a surface treatment agent. rice field. Table 2 shows the test results.

[Examples A5 to A6]
The same operations as in Examples A1 and A2 were performed except that the surface-treated calcium carbonate particles were changed to 70 parts by mass and the polypropylene homopolymer was changed to 30 parts by mass. Table 1 shows the test results.

[Comparative Example 5]
The same operation as in Comparative Example 2 was performed except that the surface-treated calcium carbonate particles were changed to 70 parts by mass and the polypropylene homopolymer was changed to 30 parts by mass. Table 2 shows the test results.

[Example A7]
The same operation as in Example A6 was performed except that the amount of the sulfonic acid-based surface treating agent during the surface treatment was changed to 1 part by mass. Table 1 shows the test results.

[Example A8]
sodium p-toluenesulfonate (sulfonic acid-based surface treatment agent-3) instead of 3 parts by mass sodium cumenesulfonate (Tayka Tox (registered trademark) N5040, active ingredient about 40%; sulfonic acid-based surface treatment Agent-5) Surface-treated calcium carbonate particles were prepared in the same manner as in Example A3 except that 5 parts by mass of agent-5) was used. Using 70 parts by mass of the obtained surface-treated calcium carbonate particles and 30 parts by mass of the polypropylene homopolymer, the same operations as in Examples A5 and A6 were performed. Table 1 shows the test results.

[Example B1]
(Preparation of resin composition for inner layer)
Heavy calcium carbonate particles having an average particle diameter of 2.2 μm (according to the air permeation method) and a specific surface area of 10,000 cm ² /g (Softon (trade name) 1000 manufactured by Bihoku Funka Kogyo Co., Ltd.; heavy calcium carbonate particles-1 ) was added to 100 parts by mass of polyoxyethylene lauryl ether phosphate (Phosphanol (registered trademark) ML-220 manufactured by Toho Chemical Industry Co., Ltd.: C ₁₂ H ₂₅ O (C ₂ H ₄ O) ₂ -P (=O) Mixture of (OH) ₂ and [C ₁₂ H ₂₅ O(C ₂ H ₄ O) ₂ ] ₂ P(=O)OH, first acid value 140 to 160; Phosphate ester-based surface treatment agent-1) 3 Together with the mass parts, the mixture was agitated for 30 minutes at a temperature of 120° C. and a rotation speed of 1200 rpm in a Henschel mixer for surface treatment.

60 parts by mass of the surface-treated calcium carbonate particles obtained above and 40 parts by mass of a polypropylene homopolymer (Prime Polypro (registered trademark) E111G manufactured by Prime Polymer Co., Ltd., melting point 160° C.) were mixed with 0.2 parts by mass of a magnesium stearate lubricant. Together with 5 parts by mass, it is put into a co-rotating twin-screw kneading extruder HK-25D (φ25 mm, L / D = 41) manufactured by Parker Corporation, extruded at a cylinder temperature of 190 to 200 ° C., cooled and cut. pelletized with

(Outer layer material)
A polypropylene homopolymer (polypropylene homopolymer, Prime Polypro (registered trademark) E111G manufactured by Prime Polymer Co., Ltd., melting point 160° C.; PP-1) was prepared.

Table 3 shows the test results.

[Example B2]
Polyoxyethylene lauryl phenol phosphate (aromatic EO phosphate, Toho Chemical Industry Co., Ltd. Phosphanol (registered trademark) LF _-200 : _{C12H25C4H4O ( C2H4O} ) _{2 -} P _{( =} O) ₍ OH) ₂ and [ _{C12H25OC4H4 ( C2H4O} ) _{2 ] 2} A mixture with P(=O)OH and a first acid value of 95-115; Table 3 shows the test results.

[Example B3]
Lauryl phosphoric acid (Toho Chemical Industry Co., Ltd. Phosphanol (registered trademark) ML-200: C ₁₂ H ₂₅ OP ( =O)(OH) ₂ and (C ₁₂ H ₂₅ O) ₂ P(=O)OH mixture, first acid value 190-210; The procedure was analogous to Example B1. Table 3 shows the test results.

[Example B4]
SOFTON 1000 was dispersed in purified water (concentration 100 g/L) to prepare a slurry. To this slurry, a sodium salt of a phosphoric acid ester having a long unsaturated aliphatic hydrocarbon chain and an ethylene oxide unit (unsaturated EO phosphoric acid ester salt, Phosphanol (registered trademark) RD-720 manufactured by Toho Chemical Industry Co., Ltd.) , Hydrocarbon chain carbon number 18, ethylene oxide unit number 7; Phosphate ester-based surface treatment agent-4) is added to 1 L of slurry (3% by mass based on calcium carbonate particles) and stirred at 50 ° C. for 30 minutes. After that, it was filtered and dried to obtain surface-treated calcium carbonate particles.
A sheet was produced in the same manner as in Example B1 except that the surface-treated calcium carbonate particles were used, and the physical properties were evaluated. Table 3 shows the test results.

[Example B5]
The same operation as in Example B1 was performed except that the surface-treated calcium carbonate particles were changed to 70 parts by mass and the polypropylene homopolymer was changed to 30 parts by mass. Table 3 shows the test results.

[Example B6]
The same operation as in Example B5 was performed except that the amount of the phosphate-based surface treatment agent during the surface treatment was changed to 1 part by mass. Table 3 shows the test results.

[Examples A9 to A13]
The procedure of Example A1 was repeated except that the amount of xylenesulfonic acid (xylenesulfonic acid-based surface treatment agent-1) was changed as shown in Table 4. The test results are shown in Table 4.

[Examples B7 to B11]
The same operation as in Example B1 was performed, except that the blending amount of polyoxyethylene lauryl ether phosphate (phosphoric acid ester-based surface treatment agent-1) was changed as shown in Table 5. Test results are shown in Table 5.

[Examples A14 to A17]
The same operations as in A1 to A4 were performed, respectively, except that the inner layer "theoretical plane occupancy TPO-actual plane occupancy MPO (%)" was "less than 2%". Test results are shown in Table 6.

[Examples B12 to B15]
The same operations as in B1 to B4 were performed, respectively, except that the inner layer "theoretical plane occupancy TPO-actual plane occupancy MPO (%)" was "less than 2%". The test results are shown in Table 7.

[Examples A18 to A20]
In the inner layer, the first outer layer and the second outer layer, the same operations as A1 to A3 were performed, respectively, except that PP-1 was replaced with the material shown in Table 8. The test results are shown in Table 8.

[Examples B16 to B18]
In the inner layer, the first outer layer and the second outer layer, the same operations as B1 to B3 were performed, respectively, except that PP-1 was replaced with the material shown in Table 8. The test results are shown in Table 8.

As shown in the table, the laminated sheet satisfying the requirements of the present invention was excellent in all of the appearance of the resulting molded product, and the moldability and mechanical properties of the laminated sheet.
As for the mechanical properties, the tests were conducted several times, and it was also confirmed that the laminated sheets satisfying the requirements of the present invention had little variation in tensile strength values.

Although data are not shown, the laminated sheet satisfying the requirements of the present invention had a good surface condition regardless of whether it was molded or not.

Claims (8)

A laminated sheet comprising an inner layer and a pair of outer layers laminated on both sides of the inner layer,
The inner layer contains an inorganic filler made of heavy calcium carbonate particles having an average particle size of 0.7 μm or more and 6.0 μm or less and a thermoplastic resin, and has a thickness of 100.0 μm or more,
The outer layer is made of a thermoplastic resin , has a thickness of 5.0 μm or more and 50.0 μm or less, and has no unevenness on the surface,
The content of the calcium carbonate particles in the inner layer is 40.0% by mass or more and 80.0% by mass or less,
The calcium carbonate particles are surface-treated with a surface treatment agent containing at least one of sulfonic acid and its salts , or a phosphate ester,
The thickness ratio of each outer layer constituting the pair of outer layers is 2.0% or more and 20.0% or less with respect to the total thickness of the laminated sheet ,
The measured plane occupation ratio MPO of the inorganic filler in at least one cut surface of the inner layer is 2 more than the theoretical plane occupation ratio TPO of the inorganic filler in the cut surface calculated based on the content ratio of the inorganic filler in the inner layer. % lower,
Laminated sheet. The laminate sheet according to claim 1, wherein the thermoplastic resin is polypropylene resin and/or polyethylene resin. The polyethylene-based resin includes high-density polyethylene and linear low-density polyethylene,
MFR (190 ° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) of the high-density polyethylene is 5 g / 10 minutes or more and 15 g / 10 minutes or less,
MFR (190 ° C., 2.16 kg) according to JIS K 6922-1 (ISO1133) in the linear low density polyethylene is 0.5 g / 10 minutes or more and 1.5 g / 10 minutes or less,
3. The laminate sheet according to claim 2, wherein the mass ratio of said high density polyethylene and said linear low density polyethylene is 90:10 to 50:50. The thermoplastic resin contained in the inner layer is a polypropylene resin,
The laminate sheet according to claim 1, wherein the polypropylene resin is a polypropylene homopolymer and/or a polypropylene block polymer. 2. The method according to claim 1, wherein the sulfonic acid is one or more sulfonic acids selected from the group consisting of alkylsulfonic acid, alkylbenzenesulfonic acid having an alkyl group of 2 or more carbon atoms, toluenesulfonic acid, and xylenesulfonic acid. Laminated sheet as described. 2. The laminated sheet according to claim 1, wherein said phosphate ester is polyoxyethylene lauryl ether phosphate. The laminate sheet according to any one of claims 1 to 6 , wherein the laminate sheet is a laminate sheet for vacuum forming. A food packaging container molded from the laminated sheet according to claim 7 .